Hitherto, in order to form a thermal oxide film on the surface of a silicon single crystal wafer, e.g., silicon single crystal wafer is mounted on a heat treatment jig (frequently referred to as wafer boat) made of heat resistant material (e.g., quartz or SiC) to set such a jig within a tube for heat treatment furnace to perform heat treatment under oxidizing atmosphere.
Control of film thickness of the thermal oxide film formed in this way is performed after subjected to calculation by the kind of the heat treatment atmosphere, the heat treatment temperature and/or heat treatment time.
In regard to film thickness of thermal oxide film to be formed on the surface of the silicon single crystal wafer, although depending upon the purpose, in the case of fabricating a bonded SOI wafer including a thick buried oxide film layer (BOX layer) as described in the Patent Literature 1, a thick thermal oxide film is formed on at least one of two silicon single crystal wafers to be bonded and a bonding process is performed.
For the purpose of forming such a thick oxide film, high temperature/long time heat treatment is performed under the atmosphere including water vapor such as wet O2 oxidation or pyrogenic oxidation, etc. as the heat treatment atmosphere where oxidation rate is high.